Method of fabricating crystalline island on substrate

Abstract

Certain electronic applications, such as OLED display back panels, require small islands of high-quality semiconductor material distributed over a large area. This area can exceed the areas of crystalline semiconductor wafers that can be fabricated using the traditional boule-based techniques. This specification provides a method of fabricating a crystalline island of an island material, the method comprising depositing particles of the island material abutting a substrate, heating the substrate and the particles of the island material to melt and fuse the particles to form a molten globule, and cooling the substrate and the molten globule to crystallize the molten globule, thereby securing the crystalline island of the island material to the substrate. The method can also be used to fabricate arrays of crystalline islands, distributed over a large area, potentially exceeding the areas of crystalline semiconductor wafers that can be fabricated using boule-based techniques.

I claim: 
     
       1. A method of fabricating a crystalline island of an island material, the method comprising:
 depositing the island material on a substrate; 
 heating the substrate and the island material, the heating melting the island material to form a molten corpus, the heating also forming a molten disk comprising oxygen and the island material, the molten disk disposed between the molten corpus and the substrate; and 
 cooling the substrate, the molten corpus, and the molten disk to crystallize the molten corpus to form a crystallized corpus, at least a portion of the crystallized corpus forming the crystalline island of the island material. 
 
     
     
       2. The method of  claim 1 , further comprising planarizing at least a portion of the crystalline island to expose a cross-section of the crystalline island. 
     
     
       3. The method of  claim 1 , further comprising, after the cooling:
 over-coating the crystalline island and the substrate with an over-coating layer to form a stack; and 
 planarizing the stack to expose a cross-section of the crystalline island. 
 
     
     
       4. The method of  claim 1 , further comprising, before the depositing:
 forming an oxide layer on the substrate; and 
 
       wherein:
 the depositing comprises depositing the island material on the oxide layer; and 
 the molten disk comprises the oxide layer in a molten state. 
 
     
     
       5. The method of  claim 4 , wherein the forming the oxide layer comprises depositing on the substrate the oxide layer comprising an oxide of the island material. 
     
     
       6. The method of  claim 5 , wherein the depositing comprises depositing the oxide layer according to a predetermined pattern. 
     
     
       7. The method of  claim 4 , wherein the forming the oxide layer comprises:
 depositing the island material on the substrate according to a predetermined pattern; and 
 oxidizing the island material. 
 
     
     
       8. The method of  claim 4 , wherein the heating comprises heating the substrate, the island material, and the oxide layer in a non-oxidizing atmosphere. 
     
     
       9. The method of  claim 1 , further comprising one or more of, before the depositing:
 polishing the substrate according to a predetermined pattern; and 
 roughening the substrate according to the predetermined pattern. 
 
     
     
       10. The method of  claim 1 , wherein the substrate comprises alumina. 
     
     
       11. The method of  claim 10 , wherein the molten disk further comprises aluminum originating from the substrate. 
     
     
       12. The method of  claim 1 , wherein the island material comprises silicon and the heating comprises heating the substrate and the island material to at least about 1500° C. 
     
     
       13. The method of  claim 1 , wherein:
 cooling the molten corpus forms a first solid portion distal from the substrate and a second solid portion proximal the substrate, the first solid portion separating spontaneously from the second solid portion during the cooling, the second solid portion forming the crystalline island. 
 
     
     
       14. The method of  claim 1 , wherein the depositing comprises:
 positioning a template on a surface of the substrate, the template comprising a channel having a first end abutting the surface and a second end opposite the first end, the surface capping the first end; and 
 filling at least a portion of the channel with the island material. 
 
     
     
       15. The method of  claim 14 , further comprising:
 after the cooling, removing the template from the substrate. 
 
     
     
       16. The method of  claim 15 , wherein after the removing, a first portion of the crystallized corpus remains on the substrate to form the crystalline island and a second portion of the crystallized corpus remains in the channel. 
     
     
       17. The method of  claim 14 , wherein the channel comprises:
 a first region proximate the first end, in the first region the channel having a first cross-sectional area; and 
 a second region distal from the first end, in the second region the channel having a second cross-sectional area, the first cross-sectional area different from the second cross-sectional area. 
 
     
     
       18. The method of  claim 17 , wherein an inner surface of the channel defines a vertex separating the first region from the second region. 
     
     
       19. The method of  claim 14 , wherein:
 the template further comprises one or more further channels, each further channel having a corresponding first end abutting the surface and a corresponding second end opposite the corresponding first end, the surface capping the corresponding first end; and 
 the depositing further comprises filling at least a portion of the one or more further channels with the island material. 
 
     
     
       20. The method of  claim 14 , wherein the second end is in communication with a reservoir configured to store the island material for at least partially filling the channel with the island material. 
     
     
       21. The method of  claim 20 , wherein the reservoir is integrally formed with the template. 
     
     
       22. The method of  claim 20 , wherein the reservoir comprises a crystallization initiator, the crystallization initiator comprising one or more of a depression into and an extension from a reservoir surface, the crystallization initiator configured to come into contact with the molten corpus and initiate crystallization during the cooling.